Amphenol RF Connector Training Course Sept. 9, 2002

However, first we should discuss There are basic RF questions that should be asked before helping a customer choose a connector However, first we should discuss Why is it necessary to ask these questions? The Sales Engineer must be able to speak to the customer and understand his needs A basic understanding of RF as it relates to helping the customer choose a connector is essential to accomplish this The Sales Engineer is the means by which this information is transmitted from the customer to the design engineer Clear, specific information leads to quick, correct designs Time is lost if the sales engineer doesn’t ask the customer these questions, because then the design engineer will have to. If the design engineer doesn’t ask, then the customer may not get what he wants. You go into a showroom to buy a car. Don’t you tell the salesman what color you want, ABS, AM FM CD Stereo, 4 wheel drive, etc? The sales engineer must transmit this information to the factory, so the customer gets what exactly he wants and needs. In the connector business, it’s not just a BNC Plug for some new cable. There is more to it than that. Perhaps, all of the questions don’t have to be asked every time in every situation, but a clear understanding of the RF aspects of connector design will help you decide when and where each question is appropriate.

Understanding RF and how it relates to cable and connectors Transmission Lines Impedance Frequency Range Return Loss-VSWR Insertion Loss Passive Intermodulation Distortion Power Handling-Voltage Isolation-Crosstalk RF Leakage Cable Assembly Amphenol RF Design Engineering Support and Capabilities I want to familiarize you with these concepts and give you enough of a basic understanding to be able to speak to engineers and help guide them through the process of choosing the correct connector for their application. Or perhaps they’ve already decided. You should be able to determine if they’ve made the correct decision.

Connector Anatomy What is a Connector? A connector is a device used to connect to cables or other devices through which electromagnetic energy is transferred from one place to another Body-Contact-Insulator Body The number 1 guiding factor Insulator Contact

Connector Anatomy Lots of changes in a very short length Mechanical rigidity Hold Contacts in place Prevent Insulator rotation or lateral movement Adapt to different cable sizes Transform between connector series Creates many impedance variations or discontinuities in a very short distance Reflections are important, Attenuation not as important The number 1 guiding factor

Connector Anatomy Various Captivation Methods Barbs Grooves Shoulders Knurls Staking The number 1 guiding factor

Connector Anatomy Contact Barb Slotted Contact Dielectric Support Bead The number 1 guiding factor Discontinuity Compensation Steps

Cable Anatomy What is Cable? Cable is a transmission line through which electromagnetic energy is propagated and transferred from one place to another Jacket-Braid-Shield-Dielectric-Center Conductor Conductor The number 1 guiding factor Jacket Dielectric Shield Braid

Cable Anatomy No changes in a very long length No impedance changes or discontinuities Usually very few reflections, but Attenuation is important The number 1 guiding factor

Assistance on the Web Amphenol RF Newsletter Technical Questions: http://www.amphenolrf.com/rf_made_simple/techquestions.asp VSWR Conversion Charts: http://www.amphenolrf.com/rf_made_simple/vswr.asp Glossary: http://www.amphenolrf.com/rf_made_simple/glossary.asp The number 1 guiding factor

# 1. Transmission Line What is a transmission line? A transmission line is a conduit by which electromagnetic energy is transferred from one place to another Coaxial Cable- Unbalanced Line: Center conductor surrounded by a concentric dielectric and outer conductor-Most popular type of transmission line The number 1 guiding factor

# 1. Transmission Line What is a transmission line? A transmission line is a conduit by which electromagnetic energy is transferred from one place to another Waveguide: Rectangular, Circular

# 1. Transmission Line What is a transmission line? A transmission line is a conduit by which electromagnetic energy is transferred from one place to another Planar Transmission Line: Microstrip, Stripline, Coplanar waveguide are most common

. . # 1. Transmission Line What is a transmission line? A transmission line is a conduit by which electromagnetic energy is transferred from one place to another Twin Line- balanced line: two parallel conductors separated by a dielectric . .

# 1. Transmission Line The type of transmission line will determine the connector style Cable Connector-Coaxial Cable, Twin Line Surface Mount Connector-Microstrip Tab Launch Connector-Microstrip, Stripline, Coplanar End Launch Connector-Microstrip, Coplanar Pin Launch Connector-Microstrip, Stripline, Coplanar

# 2. Impedance OK. So you have an equation, but what is it? Ohm’s Law

Coaxial Line Equivalent Circuit # 2. Impedance What is the Characteristic Impedance? The ratio of Voltage to Current at any point in a transmission line A transmission line can be represented as shown, with the values of C. L, R, and G determining the impedance The number 2 guiding factor Coaxial Line Equivalent Circuit

# 2. Impedance 50 and 75 Ohms are the most common impedances Do not confuse impedance with LOSS: A 50 ohm impedance does not have less loss than a 75 ohm impedance. It is not like resistance Impedance is independent of the length of the cable or connector Impedance is independent of frequency The Impedance will help determine the connector series Some series are only one impedance: C, SC, HN, 7-16 Some series can be both 50 or 75 ohms: BNC, TNC, N

# 2. Impedance Characteristic Impedance is determined by the geometry and dielectric constant of the transmission line Impedance of Coaxial Cable: Zo=(138/(E))*log(D/d))= (L/C) L=.0117*Log (D/d) uh/inch C=.614*E/Log (D/d) pf/inch

Coplanar (and grounded coplanar) waveguide, which are planar structures, often use end launch style connectors.

Stripline lines usually utilize tab or pin style launches

# 2. Impedance

# 2. Impedance Non-Constant 50, 75 ohm 50 ohm 75 ohm Impedance: The impedance of the connector generally must match that of the transmission line Non-Constant 50, 75 ohm 50 ohm 75 ohm BNC Twinaxial BNC 7/16 1.6/5.6 UHF SMB C, SC, HN Type F Twinaxial MCX Mini-UHF Type G 1.0/2.3 MMCX TNC SMA N Outer Diameter Inner Diameter Dielectric Constant Impedance .063 .020 2.0 50 Ohms .063 .012 2.0 75 Ohms .276 .120 1.0 50 Ohms

# 3. Frequency Range Frequency is the number of electromagnetic waves that pass a given point in 1 second Hertz is the unit of frequency measurement Generally, the RF performance of a connector degrades as the frequency is increased (c=f) Wavelength decreases, therefore smaller disruptions cause more problems Specifying the frequency will make it easier for the design engineer to optimize the performance Whenever possible, don’t specify a high frequency connector when a low frequency connector will work do the job All things being equal, lower frequency connectors are generally less expensive than high frequency connectors. This could give you a cost advantage over a competitor.

# 3. Frequency Range If a frequency range is not specified, then the connector will be designed to catalog specs and this could cause the design process to take a lot longer For example-A customer needs a new SMA to operate up to 12 Ghz. The catalog specifies 18 Ghz for some SMA connectors. If the connector is optimized for 18 Ghz, it will likely take a lot longer than necessary to design Give as much information about the application of the connector to the design engineer as possible Is it used in a high power, narrow frequency band amplifier? Is it used in a band pass filter? When frequency information is not supplied, or we can’t get any, we default to the catalog specs.

# 3. Frequency Range Giga = 1,000,000,000 Billion Mega = 1,000,000 Million Kilo = 1,000 Thousand Milli = 1/1000 One thousandth Micro = 1/1,000,000 One millionth Nano = 1/1,000,000,000 One billionth Pico = 1/1,000,000,000,000 One trillionth

Digital (PCS) Phone 1850 - 1990 MHz Radar 6 - 26 GHz Some Typical Frequencies: House current 60 Hz in the US (50 Hz in many other countries) AM Radio 500 - 1500 kHz Shortwave Radio 10 MHz TV (channels 2-13) 60 - 250 MHz Cellular Phone 824 - 894 MHz Digital (PCS) Phone 1850 - 1990 MHz Radar 6 - 26 GHz Direct Broadcast Satellite (DBS) 12 GHz

Frequency Chart (GHz)

# 4. Return Loss or VSWR A measure of how much power is reflected Return Loss: The portion of a signal that is lost due to a reflection of power at a line discontinuity. Return Loss is similar to VSWR and is generally preferred in the CATV industry to a VSWR specification VSWR: Acronym for Voltage Standing Wave Ratio. VSWR is the ratio of voltage applied to voltage reflected. It is the major factor contributing to the total signal efficiency of the connector. Best performance is achieved when the impedance of the cable and the connector are the same (matched) Even if the all of the transmission lines are all 50 ohms, the changes going from one to another cause reflections.

# 4. Return Loss or VSWR Reflections are created by deviations from the characteristic impedance caused by: variations in machining tolerances Variations in the dielectric constants of insulators transitions within the connector: transitioning from the cable size or stepping the connector from one line size to another line size

# 4. Return Loss or VSWR Reflection Coefficient is the basic measure of reflection: r=abs(Zo-Zl/Zo+Zl) where Zo is the characteristic impedance and Zl is the actual impedance Generally, this is the most important RF figure of merit for a connector VSWR=(1+r)/(1-r) Return Loss=-20*log (r), in dB (decibels) These are all the same thing, just expressed in different ways Return Loss and VSWR are most commonly used

Return Loss = Ratio of reflected to incident power in dB Component Cable Power transmitted into component Incident Power Reflected Power Return Loss = Ratio of reflected to incident power in dB VSWR = Ratio of maximum to minimum electric field (Voltage) Rope tied to a post-sets up standing wave if continuous pulses are sent down the line

Relative Magnitudes: Power Power Transmitted Return Reflected into Component Loss VSWR 1% 99% 20 dB (1/100=10-2) 1.25 5% 95% 13 dB 1.58 10% 90% 10 dB (10/100=10-1) 1.95 50% 50% 3 dB 5.80 Try to get a realistic idea of the Return Loss really required for a specific application Trying to design very low VSWR connectors, when not really needed, can take a long time and can add to the cost

dB Notation Increase Decibel (dB) of Signal Equivalent 1 = 100 = 0dB 2 = 100.3 = 3dB 10 = 101 = 10dB 20 = 101.3 = 13dB 100 = 102 = 20dB 1000 = 103 = 30dB 1/10 = 10-1 = -10dB 1/100 = 10-2 = -20dB 1/1000 = 10-3 = -30dB Rather than say “The gain of the amplifier is 100 times”, we say, “The gain is 20 decibels.”

# 5. Insertion Loss IL = -20*log (Pout/Pin) Insertion Loss is expressed in dB, and is a measure of the total loss of power going through a device IL = -20*log (Pout/Pin) Includes losses due to reflection (usually the dominant factor unless the Return Loss is very low <-26 dB), plus losses due to the dielectric and metal conductors (Attenuation) Long Cable assembly-Connector insertion loss not usually significant Short cable assembly- Connector insertion loss can be significant Typically, connector insertion loss is very small (.1-.25 dB) Whatever power is not reflected will go on through the connector. Some of what goes through it will be lost due to heating effects.

# 5. Insertion Loss As frequencies increase, the insertion loss increases (as a square law function (P=E^2/Z) Most of the electromagnetic energy (current) travels through the conductors in a circumferential ring Most of it in center conductor, but there is some impact from outer conductor Current flow is restricted to the surface layer or “skin” of the conductor Approximately 98% of the current density travels within 4.6 skin depths The reason higher frequencies are continually pushed out from the center of the conductor to their ride depth (the "skin" of the wire) is due to a force, which is produced by the rapidly fluctuating AC current. This force is a result of self-inductance which is a phenomenon resulting in the opposition to a change in direction of a signal (AC) due to locally circulating "eddy currents." Therefore, the deeper the frequency penetrates, the more it is damped, until it reaches an energetic equilibrium, which becomes its depth of penetration or "ride depth". This is analogous to the way quicker temperature changes penetrate a shorter distance into thermal-conductors than slower ones per unit of time. This "skin depth" is often decided on from a common formula; (depth of penetration=1/sq root (frequency*pi*magnetic permeability*conductivity) to calculate the depth to which, for example, a 20K frequency will penetrate. From this formula it is evident that Silver wires actually have an even shorter depth of penetration necessitating even smaller conductors than copper! This is because of the different conductive characteristics of Silver.

# 5. Insertion Loss The length of the connector and the materials chosen will impact the insertion loss shorter is better Plate the conductors with a high conductivity material Nickel-Inexpensive, hard material with good conductivity, but high relative permeability resulting in higher insertion loss Gold-Hard material and an excellent conductor, but expensive Silver-Excellent conductor, less expensive than gold, better permeability than nickel, but softer, and tarnishes Stainless Steel-Rugged material for small connectors such as SMA, but steel has high relative permeability

# 5. Insertion Loss

# 6. Passive Intermodulation Distortion Not well known until mid 1990’s Primarily concern to satellite, microwave relay industries Modern Frequency plans High Power levels Sensitive Receivers Spurious Signals created by non-linear mixing of 2 or more frequencies in a passive device Active PIM-generated by amplifiers-is reduced by filtering Passive PIM-filtering not possible Common to many channels Must be low PIM designs

# 6. Passive Intermodulation Distortion Spurious Signals created by non-linear mixing of 2 or more frequencies in a passive device PIM products fall in receive (uplink) band Block Channels 3rd order generally greatest amplitude 5th and 7th may be of concern fIM = mf1 +/- nf2 (2f1-f2), where m = 2 and n = 1 is a 3rd order product If the circuit has non-linear characteristics, then the fundamental frequency components will become distorted in the time domain and generate a decaying series of higher order harmonic frequency components in the frequency domain.

# 6. Passive Intermodulation Distortion F1 = 930 Mhz and F2 = 955 Mhz, then Fim = 905 Mhz

# 6. Passive Intermodulation Distortion Base Station Antenna Systems Simplex- Most prone to PIM effects Most economical Duplex Less Prone to PIM More expensive Cross Polarization Least PIM susceptible May require more space

# 6. Passive Intermodulation Distortion dBm-measure of power relative to 1 milliwatt dBc-measure of dB below a specified carrier level +43 dBm input PIM: -120 dBm Spec: -163 dBc Common Spec is -143 to -163 dBc (-100 to -120 dBm)

# 6. Passive Intermodulation Distortion Causes of PIM Poor Contact Junctions-Non linear rectifying Solder outer-Solder inner- over molded design are best Most stable Ferromagnetic materials-Non-linear hysteresis No Nickel, Stainless Steel Contamination Types of Connectors 7-16 DIN Type N TNC-Occasionally Never use Bayonet (BNC) or Push on styles Poor Contact Junctions Insufficient contact pressure irregular contact surfaces oxidation-causes metal/oxide junction contact impurities corrosion Small separation of contact surfaces causes tunneling (diode) effect Ferromagnetic Materials Nickel, steel 50 dB (or more) degradation in PIM level Contamination-Metal particles Cable Trimming-Flakes from copper jacket Flux Particles adhere

# 7. Power Handling Capability There are 2 types of power handling (expressed in watts) that must be considered Average Power Peak Power Average Power-the input power to a cable/connector which will produce a maximum safe center conductor temperature under steady state conditions when terminated with a matched load. A safe center conductor temperature is one that will not melt the dielectric Average Power-This cable practice-relating power ratings to the devices' ability to dissipate heat-provides a basis for connector power ratings. Retaining the idea of heat dissipation, it is evident that a connector of a geometry which approximates its associated cable will have at least an equal power rating if the connector dielectric is the thermal equivalent of the cable dielectric. Generally, a connector will have a higher power rating since one or more of the following situations normally occur: 1. Connectors having metallic shells dissipate heat at a greater rate than a dielectric jacketed cable. 2. Connectors are attached to good heat sinks-transmitters, antennas, bulkheads, etc. 3. Connectors generally have a lower attenuation per unit length than cables; hence, heat generated per unit length is less.

# 7. Power Handling Capability Average Power is inversely proportional to frequency and must be derated accordingly Average Power=Power Rating @ 1 Mhz/ (Frequency in Mhz) Connectors generally have higher power ratings than the cable to which they are attached They have metal shell-cables have braids covered by plastic jackets They can be attached to bulkheads which help dissipate heat They usually have lower attenuation per unit length due to air sections within the connector I completed a Power Ratings spreadsheet several months ago and it is supposed to be put up on the website

# 7. Power Handling Capability Peak Power-is limited by the voltage rating of the connector. The peak power is determined by the equation V^2/Z where V=the peak voltage rating and Z is the characteristic impedance Peak Power is not a function of frequency Peak Power is an inverse function of VSWR and modulation schemes and must be derated Peak and Average Power are functions of altitude and must be derated accordingly Maximum power ratings will always be the lesser of the cable/connector combination The voltage at which a connector will break down is generally independent of frequency but varies as a function of altitude and should be derated. In addition, VSWR and modulation schemes will have an impact on the peak power level.

Max. Operating Voltage (volts) Used to determine Peak Power Ratings This information is in the catalog Not breakdown or Hipot values, but use operating voltages. These are long term capabilities. Hipot values are a 1 minute test

# 8. Isolation-Crosstalk Isolation and Crosstalk are used interchangeably They are a measure of how much signal is picked up by an adjacent line Ganged style connectors on PC boards Harnessed or “parallel run” cable assemblies They are measured in dB and usually range from –60 to –100 dB If frequency increases or the length of the lines increase, crosstalk gets worse If the distance between the lines increases, crosstalk gets better If frequency increases, crosstalk gets worse If the distance between the lines increases, crosstalk gets better

# 8. Isolation-Crosstalk There will be significant crosstalk between the lines on this ganged connector unless some precautions (such as shielding) are taken Customer wanted –80 dB @ 1 Ghz Even with a shielded cover on the back, could only achieve –60 dB due to spacing required by the customer between the lines. Customer would have to look at his design requirements. This example was simulated using HFSS

Question # 9. RF-Leakage RF Leakage is a measure of how much signal leaks out from a connector in dB at both the interface and at the cable entry As frequency increases, the leakage gets worse Typical RF Leakage values range from –40 dB for Push-On types to -90 dB for threaded styles on Semi Rigid cables Generally not a big concern except if epoxy captivation is used

#10: Is the connector used on a cable assembly 2 connectors separated by a distance on a cable At specific frequencies, all of the reflections can add up (both connectors and cable) When specifying a connector for a cable assembly, the cable assembly requirements must be known Catalog connectors, even if performance levels meet MIL Spec requirements, may not be able to perform to the cable assembly specifications

#10: Is the connector used on a cable assembly Calculate the total worst case VSWR by multiplying all of the VSWR’s: For example- The cable assembly specification is 1.45 maximum 1st connector VSWR=1.25 2nd connector VSWR=1.15 Cable VSWR=1.05 Total worst case VSWR=1.25*1.15*1.05=1.51 Choosing a catalog BNC connector with a VSWR=1.25 and a catalog SMA connector with a VSWR of 1.15 obviously won’t work. Special connectors are needed.

#10: Is the connector used on a cable assembly Shows the interaction (addition and subtraction) of the VSWR of the connectors on each end and the cable. The longer the cable assembly, the less impact the second connector has due to the attenuation of the cable. Reflections from the second connector are attenuated by the length of cable. 3 dB of cable attenuation creates a 6 db round trip loss for the second connector reflections.

#11: How can Amphenol RF adequately support the design and development of high performance, RF connectors? RF Design Capabilities ANSOFT High Frequency Structure Simulator Test Capabilities-Design Verification Network Analyzers PIM Test Capabilities I’ve got the answers to all of my RF questions. Now what can the design engineer do to support me in the field?

RF Simulation Capability ANSOFT 3D High Frequency Structure Simulator Model any Geometry No Frequency Limitation S Parameter Analysis Return Loss, VSWR, Insertion Loss etc. Radiated Power E Field Plots Time Domain Analysis Optimization Capability

RF Simulation Capability The connector is designed using standard RF practices and 2D linear analysis programs for “ballpark” performance Calculate impedances within the connector Calculate nominal compensation steps within the connector Draw the problem in HFSS-import from PRO-E: IGES (3D), or DXF (2D)File Assign the materials Set the ports and boundary conditions (symmetry) Solve Analyze frequency and time domain plots Compensation step-an introduction of a high impedance within the connector to compensate for capacitances created when changing from one transmission line size to another. SMA-SMB adapter

RF Simulation Capability Draw the RF Model from the Mechanical drawing

RF Simulation Capability Plot the desired S Parameters

RF Simulation Capability View Time Domain response to determine the location of impedance mismatch Time domain is the inverse of the frequency domain. You can see the reflections as a function of distance. Compare the location of the reflections on the plot with the internal geometry of the connector to locate discontinuities

RF Simulation Capability All design changes are made on the computer (No samples made until the design is optimized) Simulations in a matter of minutes, or hours at most Numerous iterations in a matter of hours or days Final modifications (if needed) made after testing Examples on following slides

Surface Mount Connector on Microstrip Customer must supply board characteristics: Thickness Trace width Material (dielectric constant) Transmission line type (i.e.. Microstrip, stripline) Surface Mount connector on Microstrip board Customer needs to supply board parameters Connector exhibits excellent Return Loss, but when mounted on board, is not very good Connector has excellent Return Loss (-35 to –40 dB) When mounted on board, performance deteriorates (-20 dB) due to the mismatch at the launch

Surface Mount Connector on Microstrip Initial simulation results Return Loss Insertion Loss

Surface Mount Connector on Microstrip .010 wide .015 wide .022 wide Try several different launch configurations to achieve less reflection Capacitance due to launch Modify launch area to reduce the negative (capacitive) discontinuity at the launch area Time Domain

Surface Mount Connector on Microstrip Final Insertion Loss Final Return Loss Return Loss Insertion Loss Able to achieve a significant improvement in Return Loss and Insertion Loss by modifying the launch area

Antenna Isolation Board Design Capabilities are not limited to connectors Can model and simulate entire assemblies Example: MCX angle PC connector on a capacitively coupled microstrip board 4” of RG-316 cable Straight MCX connector and angle MCX PC connector on ends of cable

Antenna Isolation Board 919-101P-51SX 4” RG-316/U Board, Top View .063 thick, FR4 47pf, 4000 V, capacitor 919-134C-51P1X .115 wide trace 919-119J-51AX

Antenna Isolation Board Board, Bottom View Ground Plane 47 pf Cap, 4000 V, capacitor

Antenna Isolation Board (Simulated vs. actual test results) Return Loss Insertion Loss Spec: -15 dB Return Loss and -1.5 dB Insertion Loss at 900 Mhz

Example: Angle Plug for LMR400 Cable VSWR Improvement Contact too close to body Initial VSWR Can tell there are problems with this design just by looking at the drawing 5 mm Diameter too small (35 ohm impedance) ANSOFT HFSS Model

Angle Plug for LMR400 Cable VSWR Improvement Recommended Design Changes Remove Chamfer at solder post on contact Increase 5mm diameter to 6.3 mm diameter on Body Remove chamfer and shorten contact by 1.25 mm We know where the problem is, ANSOFT tells us how much to correct. Increase diameter to 6.3 mm ANSOFT Model Final improved VSWR

Test Capability-S Parameters State of the art Network Analyzers HP 8510: 26.5 Ghz Vector Network Analyzer HP 8753D: 50 Ohm 6 Ghz Vector Network Analyzer HP 8753D: 75 Ohm 3 Ghz Vector Network Analyzer Return Loss Insertion Loss VSWR Crosstalk RF Leakage

Vector Network Analyzer (S Parameter Measurements) RF Leakage Test chamber

Passive Intermodulation Distortion Testing There are no “high tech” computer programs to predict IMD performance Devices must be built and tested State of the art measurement test set using 20 watt (+43 dbm) signals with a system noise floor of -130 to -135 dbm Computer Automated-in house programming capabilities to customize test measurements Typical specifications of –116 to –120 dBm for 7-16 and Type N connectors on helical and annular cables

PIM Testing – Cont’d

PIM Testing – Cont’d Computer Control (HP VEE Interface)

How to Select an RF Connector Select a connector based on the information learned from asking questions about the 10 RF parameters: 1. Impedance Typical impedance of a system is 50 or 75 ohm. See Overview in catalog for impedance by series. 2. Frequency Range Connector series range from 100 MHz to 26.5 GHz. See Overview in catalog for frequency range by series. 3. Cable Type Connector series are designed to terminate to a limited number of cable types. Is it a new cable required by the customer? Is it a PC style? See the “Cable Selection Chart” in the catalog. 4. Electrical/Mechanical requirements VSWR, Voltage Rating, Temperature Range, and other environmental requirements are all key specifications. 5. Coupling Type Choose between Threaded, Bayonet, Snap-on, and Push-pull based on all of the above. Use the catalog to help zero in on the final choice

Use all of the information gathered to make a final decision Coupling style Frequency range: 6 Ghz Power Handling: 5 Watts Average RF Leakage: -70 dB (Eliminates Push on or Bayonet styles) PIM requirements: -None Connector style Impedance: 50 Ohms Return Loss: -20 dB Insertion Loss: -.1 dB Mechanical Restrictions Available Real Estate: .5 “ long Cable: RG-142 Cost, other mechanical requirements, etc. N, TNC, SMA, 7-16 SMA, TNC Final Connector Choice